UR-73 -1603
UR-73 -1603a . d7’3///4.5 ’ENGINEERING DESiGN CONSIDEIUITICINSFOR LASERCONTROLLED THERMONUCLEAR REACTORS*James M. Williams, F. T’.Finch, T. G. Frank, and J. S. GilbertUniversity of California, Los Alamos Scientific LaboratoryP. O. Box 1663, Los Alamos, New Mexico87544During the brief history of Laser Controlled Thermonuclear Reactor (LCTR)concepts, there has been little opportunity to do more than identify some of1,2Primary efforts have been dedithe important engineering design problems.cated to assessing the feasibility of laser compression and heating of DTpellets to thermonuclear ignition and burn conditions. The current pace ofdevelopment of laser-driven fusion, together with the urgency of providing sourcesof safe, clean, low-cost electrical energy have prompted more serious recentconsiderationof engineered power reactor systems.Thermonuclear energy released from fusion pellet microexplosions must becontained in a manner that both prevents excessive damage to reactor componentsand permits efficient recovery of the energy for power production. Reactorcavities are surrounded by relatively thick blanket regions containing lithiumfor breeding tritium and for circulating lithium coolant.Theoretical investigations indicate that very short, high-power laser pulsesare necessary for compression and heating of DT pellets. Laser energy must betransported to and focused on small DT pellets at the center of each reactorcavity. Reactor cavities with multiple penetrations for s etricallyarrangedlaser beams are in the early conceptual design stages.Cryogenic fuel-pellet injection systems in close proximity to relativelyhostile cavity environments may be necessary. High velocity injection willprobably be necessary to minimize heatir of pellets during injection and tomaintain stable trajectories.CHARACTERIZATIONOF DT PELLET MICROEXPLOSIONSReference design LCTR studies have been.conducted based on a pellet yield of100 MJ.Energy release yields and spectra from bare DT pellets have been esthatsdanalytically; typical results for a 100 MJ pellet icroexplosian are summarized*work performed uni,erthe auspices of the U. S. Atomic Energy Commission, ContractNumber W-7405-ENG-36.
2in Table I.It should be emphasized that energy release yields and spectra arevery sensitive to pellet mass, composition, and temperature-densityprofilesduring the time of thermonuclear burn and may vary significantly from the resultsgiven in Table I.Although we have chosen a 100 MJ microexplosion far our initial refereuceLCTR studies, thermonuclear snergy gain as a function oi laser energy absorbed3in homogeneous, solid DT spheres have been calculated. Results of these calculations are shown inFig. 1.REACTOR CAVITY A-NDBLANKET DESIGNCurrent LCTR studies are considering several cavity and lithium-blanket designs. These designs can be categorized according to the physical processes bywhich energy deposition from pellet microexplosions is accomdated by the firstwall of the reactor cavity. Energy deposition from incident x rays, a particles,and pellet debris occurs in a very thin layer at the surface of the reactorcavity; whereas the kinetic energy of the neutrons is deposited volumetricallythroughout the blanket and reactor structure. Thus, the inner surfaces ofcavity walls to depths of a few pm must be designed to withstand energy deposition on the order of 23 MJ per microexplosion for each 100 Wpellet. Blanket-coolant regions must accept total volume energy depositions of - 77 MJ permicroexplosion in addition to heat that must be conducted through the cavitywal1.Evaporation and ablation of lithium from the cavity surface characterizes4dominant phenomena which occur in both the wetted-wall and the BLASCON concepts.These concepts are shown schematically in Figs. 2 and 3, respectively. Thereactor cavity for the wetted-wall concept is formed by a porous niobium wallthrough which coolant lithium flows to form a protective coating on the insidesurface. The protective layer of lithium absorbs energy of the a particles andpellet debris and part of the x-ray energy, is vaporized and ablates into the.reactor cavity and is subsequently exhausted through a supersonic blowdownnozzle. The ablative layer is restored between pulses by radial inflow of.lithium from the blanket region.In the BLASCON concept, a cavity is fo ed by a vortex in a rotating poolof lithium in which pellet rnicroexplosionstake place. Rotational velocity isimparted to the circulating lithium by tangential injection at the peripheryof the reaccor pressure vessel. Bubbles can be entrained in the rotating lithiuw.
3to atten te the shock waves created by pellet microexplosions. Energy deposition byxraysandchargedparticles results in evaporation of lithium from theinterior surface of the vortex.The possibility of lining cavities with other ablative materials, such ascarbon, is also being investigated. For such a design, a relatively small massL.,:.of cavity-line” terial would be ablated by each pellet microexplosion. Themass of material ablated depends upon characteristics of the pellet burn, ionizedpalticle ranges in the abiative material, and the cavity diameter. The cavitywall would cool sufficiently during the time intervals between successive pelletmicroexplosions to permit condensatim.Protection of cavity walls from a particles and charged particles in thepellet debris by means of a magnetic field is also a potential conceptual alternative. A very simple rendition of this concept is shown schematically in Fig.4.The reactor cavity is cylindrical in shape with an axial magnetic field.The particles and the ionized particles in the pellet debris are divertedalong magnetic field lines to energy sinks at the ends of the cavity. In theconcept shown, energy deposition in the heat sinks results in the evaporation oflithium. A staged vacuum system is shown for removal of the lithium vapor andmaintaining cavity pressure at vacuum levels at the cavity center. Minimum cavitysizes would be determined by permissible x-ray energy deposition limits oncavity walls. Cavity liners of carbon or beryllium would be advantageous forincreasing the tolerance for x rays.Major functional requirements for blanket performance include the breedingof tritium and the removal of heat.In our preliminary conceptual studies itis assuned that lithium in the blanket regions will be circulated thrcugh anintermediate heat exchanger for thermal energy removal from the reactor. Initialestimates indicate that acceptable tritium breeding ratios can be obtained fromblanket designs utilizing natural lithium for coolant and either stainless4,5steel or a refractory metal for the reactor structure.LbAlternative blanket compositions may be advantageous for some concepts,especially the magnetically-protecteddesign. Alternatives include stagna tlithium metal, lithium alloys, and lithium compounds, any of which could becombined with gas or heat-pipe cooling. In addition, circulating lithium :’altswill be considered.INOTICEThis reportWSIprepnred M an account of worktponsorod by the Unllad StmOI (lovernmant.Noltherth. Unit.d Stmtes nor th. United States Atomic EnergyCommission,nor ny of thrnlr amployces, nor any’c :thdr contractors,subcontrnctorm, or their employees,mskos any wmranty, oxprossorlmpllod,ormcumesmryl@Ilabllltyor rosporrdbllltyfor tho -ccuracy, com Platonou or unfulnemof any Informstlon,appwatus,product or procou dlsclossd, or ropraunts that Its uI#. . # -. 1-*.1----1 -------- -------, ----r.
4Many opportunities exist to apply engineering ingenuity to the design ofreactor cavities. There are economic incentives to design reactor cavities ofminimum size and for high pellet-microexplosionrepetition rates. Some of thez9 uu,r1cmore important problem areas in engineering design are directly related to cavity T.,,performance. Examples are: Evaporation and abiation of first *all materials leading to hydrodynamic effects and to stresses in reactor vessel.Evacuation of the ablated lithium from the cavities of the lithiumwetted-wall and the magnetically-protectedconcepts prior to successive pellet microexplosions. Preliminary investigations ‘idicatethat sufficiently intense, focused laser light cannot be transported16efficiently through lithium vapor at densities greater than 103 6,7atoms per cm .Restoration of the lithium vortex between pellet microexplostonsin the BLASCON concept. Experimental work is being done at theOak Ridge National Laboratory to investigate this problem.Ablative material condensation kinetics in the carbon-lined drywall concept. Complete confidence in the feasibility of this concept \:.11require extensive investigation.Design and fabrication of composite walls for the dry-wall andmagnetically-protected concepts. .Significantproblem result fromthermal-expansionand irradiation-inducedswelling mismatches betweenprotective and structural materials.Protection of pellet-injection systems am! beam-transport-system,}components from x rays, energetic charged particles, neutrons and,;cavity ablative.materials. The use of distance, magnetic fieldsand fast operating mechanical.devices is envisioned.Engineering design problems related to blanket design include thermalhydraulic requirements for adequate heat reumval, structural integrity withminimum penalties to breeding ratio, and containment of tritium. These problems,while not routine, appear to be amenable to solution with essential’‘ establishedtechnology.The design of reactor cavity, blanket and coolant systems in a manner thatpermits replacement of irradiated component:]constitutes a major engineeringproblem. Fast-neutron and charged-particle irradiation data indicate severely-.
5limited cavity-wall lifetimes for minimum-size reactors which are operated athigh power levels. The down time required for reactor maintenance, the costof auxillary equipment, and the complexity of reactor component replacementoperations will be important factors affecting optimum design choices and the.ultimate cost of power from LCTR systems.LASER SYSTEMSLaser research and development is advancing rapidly, and it is not possibleto predict the specific type or types of lasers that will be most advantageousfor application in LCTR power systems. Characteristics of two lasers which arenow being developed and which may ulthately be applicable to LCTR power production are listed in Table II.Calculations indicate that a to al laser pulseof - 1 MJ with a pulse width of - 1 nsec will be required (see Fig. 1).Thelaser system technology which is developing most rapidly and which shows promiseof achieving the required performance at reasonable cost and operating efficiencyis the C02 system.Experimental C02 lasers now in existence at LASL provide the basis fordesigning larger laser systems. The annular power amplifier design, shown8,9is an extrapolation of this work.schematically in Figs. 5 and 6,A concept.:alC02 laser design has been developed for use in reference LCTRdesign studies. The operational characteristics of the reference laser designare giv n in Table III. Eight laser-amplifierswould bt required to providethe anticipated requirement of 1 MJ per pulse.The power amplifier is pumped by an electric discharge with ionization by.an electron beam. The annular lasing cavity is subdivided into eight subcavitieswhich can be pulsed simultaneously or individually in a programmed manner.Sequential pulsing of individual cavities may provide some capability for pulseshaping by superimposing beams. Annular pulses are collected and focused bmeans of a toroidal, catoptric beam-focusing device. Laser pulse repetitio,ratee of from 35 to 50 per sec would require circulation of cavity gas for.Lrconvective cooling.At 35 pulses per see, cooling the circulating laser gas in the referencedesign laser amplifier will require - 40 of cooling capacity. Moreover,since amplifier performance is si nificantly degraded by excessive temperatures,it will be necessary t dump this heat at relatively low temperatures. Severalmanifolds of intake and exhaust ports will probably he required to permitradial flow distribution of the laser gas in the lasing cavity.
One of the most restrictive limitations on laser amplifier design is due tolaser light damage to window materials. The experimentally determined damage2threshold for the alkali halides is - 3 J per cm for repeated, short laserz1 :tupulses. In order to avoid thermal stresses in windows, it will be necessaryUdto cool th c.to prevent excessive temperature gradients. The laser-beam subsystem transports laser light from the laser power amplifier into the reactor cavities and focuses the laser pulse on fusion pellets atthe center of the cavity. Efficient beam transport requires a number of opticalcomponents and a system of evacuated light pipes. Optical elements are requiredfor:Separation of gases of different composition or pressure {windows);Beam focusing, diverging, deflection and splitting (mirrors);Fast switching of beams; andComponent isolation to decouple the laser from refle ted light.The alkali halides are tiing developed for infrared laser window materialsand typical metallic reflectors (Cu, Au, Ni, etc.) for mirrors. Research onbulk and on surface damage mechanisms is being actively pursued as is the sea chfor materials with improved performance. Limits on beau intensity are imposedby damage to windows and mirrors from laser light which results in LCTRrequirements for large diameter components. Elements for fast switching andcomponent isolation include both active elements (electro-optic,acousto-optic,expendable membranes, etc.) and passive elements (saturable absorbers anddiffraction gratings).Since the laser subsystem represents a significant fraction of the capitalinvestment of an LCTR plant, it may be economically advantageous to centralizecomponents so that each laser system serves several reactor cavities. Centralized‘:lasersystems require fast beam switching from laser power amplifiers to selec- ;tL;.ted beam orts. Beam switching, which would be required for central laser systems, might be accomplished by rotating mirrors. This scheme would requiremoving parts in a vaccum system with associa-tedrequirements for bearings andseals. Very long light pipes could also be required for large rnulticavityplants with centralized laser syst s.It will be necessary to maintain precisealignment of optical components which will require compensations for effectsof temperature changes, earth tremors and plant vibrations; and, of course, the
7laser beam transport systems must penetrate the biological shielding surrounding‘eactorcavities by indirect paths to prevent radiation streaming.Beam foc lsingon target will probably require sophisticated pointing andtracking systems with feed-back senosystems controlling large mirrors invacuum and radiation environments. The final optical surface with its.associated blow-back protection devices and contaminated vacuum and coolingsystems may have to be engineered for frequent replacmnent.F’VELCYCLE—.——cycle is the only fuel cycle which is being seriously consideredat this timeforlaser-fusion systems. Deuterium is easily and cheaply obtainedfrom conventional sources, but tritium is expensive tc produce and is notavailable in large quantities. Thus, it is expected that tritium will beproduced by reactions between neutrons and lithimin the blanket regions ofLCTR plants.In order to prevent significant loss of critium by diffusion through theintermediate heat exchanger and reactor containment, very low tritium concentrations must be maintained in the circulating lithium. This requirementfurther complicates the difficult task of separating the tritium from thelithium. Several separation schemes have been proposed but none has yet beendemonstrated to be s perior for this application.GENE—.M. LIn addition LO the complexities associated with the design of various LCTRsubsystems, there are many engineering design considerations associated withsubsystem interfaces and system design foz large power plants. In the ultimateanalysis, the performance of the reactor power plant as a whole is the mostimportant overall consideration. System studies can be useful in examining theimpact of subs stem alternatives, sizes, arrangements and the degree of necessaryredundancy provided to ensure adequate system reliability and minimum adverseimpact to the environment.Because of relatively large circulating power fractions, gross electricalpower production will be significantly larger,. than net power production; also,a significant fraction (15 to 20%) of the waste heat must be dumped at lowtemperatures. These factors may influence reactor siting decisions.CONCLUSIONSPreliminary engineering analyses of LCTR power plants ha revealed manyI-.:
8challenging engineering problems, some of which transcend present technology.However, much of the technological development which has resulted from thefission reactor and space programs is applicable to the fusion reactor programas well. Although uch analytical and experimental investigation remains tobe done, no problems have been discovered fm wnich there are not reasonableconceptual solutions. Intensive efforts to resolve tt. seengineering designproblems awaits successful achievement of thermon’lclearburn from laser fusion.REFERENCES1.L. A. Booth (Compiler), “Central Station Power Generation by Laser-DrivenFusion”, LA-4858-MS, Vol. I, Les Alamos Scientific Lab., 2/72.2.James M. Williams, “Laser CTR Systems Studies”, LA-5145-MS, Los AlamosScientific Lab., 3/73.3.J. S. Ciarke, H. N. Fisher, and R. J. Mason, “Laser-Driven Implosion ofSpherical DT Targets to Thermonuclear Burn Conditions”, Phys. Rev. Ltrs.,Vol. 30, p. 89, 1/15/73.4.A. P. Fraas, “The BLASCON - an Exploding Pellet Fusion Reactor”, ReportTM-3231, Oak Ridge National Laboratory, 7/71.5.Keith Boyer, “Laser Program at LASL - Progress Report - January throughJune 30, 1973”, IA-5366-PR, Los Alamos Scientific Lab., 8/73.6.Dale B. Henderson, “Laser Pulse Propagation Through Ionizable Media”,IA-5086-MS, Los Alamos Scientific Lab.”,12/72.7.June 29,D. J. Jackson, Los Alamos Scientific Lab., Internal Memorandum,.1973.8.R. E. Stapleton, et al., “Electron-Beam-SustainedGas Lasers: Discussionfrom the Engineering Viewpoint, Part I - Design of the LASL 1 kJ and 10 kJC02 Lasers”, paper to be presented at Fifth Symposium on EngineeringProblems of Fusion Research, Princeton, New Jersey, November 6-9, 1973.9.K. Riepe, R. E. Stapleton, J. P. Rink, “Electron-Beam-SustainedGas Lasers:Discussion from the Engineering Viewpoint - Part .I- Problems in theElectrical Design of Very High Energy.Systems”, paper to be presentedat Fifth Symposium on Engineering Problems of Fusion Research, Princeton,New Jersey, November 5-9, 1973.6t:. #.:.
rTAA2.99 W DT PELLET }lTCROE LOSIO:?.“Mechanism-.Fractionof TotalParticlesEner y ReleasePer PulseAverage EnergyPer Particle.xo.oiRays‘4 keV peak4.cxParticles that Escape Plasma0.07Plasma Kinetic Energy!).152.2x 10191.3 x 1019a Particles0.6 MeV .1.2 x 1020Deuterons0.3 MeV(Total\,:e.().37 X[Tritons1.2 x 10200.4 MeV 3.3 x 101914.1 MeV:0.77Neutrons.-- .---RactionalBurnup0.25.–-.
ICALHF W/RECYCLECHARACTERISTICSTYPICALIIET.Em,2 10 . 50,1-10 lo“.“.‘ 8.iJPULSE. ATING,ATPI PRESW?E3“5-10.#
- REFERE;4CELIESIGi/lASERSYSTEfIlDESCRWTION OF SYSTEM:——OSCILLATOR, PREAMPLIFIER.CEPT WITH THEPOWER AMPLIFIERPOWER AMPLIFIERAN TURE3:U4:1;HE:N2:C02OUTPUTPER POWER AMPLIFIEROJ25 NJi’b4BEROF SECTORS PER POWERAMPLIFIER %PULSE DU2ATIONPULSE REPETITIONOscI LMToR1 NSEC30-50SEC-lRATEMULc I-LINEMULTI-BANDSPECTRUM.BEAM FLUX ATLENGTH ANDOhTAOUTSIDEWINDOW APERTUREDIAMETER-CAVITYOF3 iCM2.3xl,5T04i’1THERMAL ENERGY REMOVAL REQUIREMENT40 flwIASER10ZENERGY OUT: ELECTRICALENERGY VI-.-.
pelletsto thermonuclearignitionand burn conditions. The currentpaceof The currentpaceof developmentof laser-drivenfusion, togetherwith theurgencyof providingsources
A-Level History, HIS1D: Stuart Britain and the Crisis of Monarchy 1603-1702 Absolutism Challenged: Britain 1603-49 Section 1: Monarchy and Parliament 1603-1629 KEY INDIVIDUALS James Stuart: King James VI of Scotland/I of England, reigned 1603-1625 Esme Stuart: Favourite from 1579-
I. The Foundations of England, 55 B.C.–A.D. 1066 II. The Submergence of England, 1066–1272 III. Emergence of the English People, 1272–1485 IV. The Progress of Nationalism, 1485–1603 V. The Struggle for Self-government, 1603–1815 VI. The Expansion of England, 1603–1815 VII. The
Among the texts that we will read will be works by Montaigne, Shakespeare, Donne, and Benjamin Franklin. All the texts will be available in English and . Translation by John Florio, London, 1603. See also Penn’s copy, Folio PQ1642.E5.F6 1603, online at . Using Florio’s and Cotton’s online translations of Montaigne’s
The Canterbury Tales The Middle Ages Period, 450-1485 The Canterbury Tales The Tudor Period, 1485-1603 Shakespeare The Stuart Period, 1603-1688 Pilgrim’s Progress The Neoclassical Period, 1688-1789 Robinson Crusoe The Romantic Period, 1789-1832 Pride and Prejudice The Victorian Period, 1832-1914 A Tale of Two Cities
LADY MARY SCUDAMORE (c.1550-1603), COURTIER. 1. by Warren Skidmore. It might be argued that Lady Mary was the most interesting woman in the late 1590s (after the queen herself) in all of England. She became th e only lady of Elizabeth’s privy chamber to have
She ruled England and Ireland from 1558, after the death of her sister, Mary I, and reigned until her own death in 1603. When did Elizabeth I become queen?
Elizabethan England, c1568-1603 (HT1- Elizabeth’s court and Parliament) Patronage; Sir William Cecil, Lord Burghley Member of the gentry.Moderate Protestant. Had experience under Edward VI. Wanted to avoid war and unite the nation. Did not make rushed decisions. The Queen
1. The Elizabethan Age, 1558-1603: How successful was the government of Elizabeth I? Timeline / Chronology Key Ideas Nov 1558 Elizabeth becomes queen Jan 1559 Elizabe
